Fixture vent sizing

I have a 1.5" pvc pipe that vents my dishwasher and kitchen sink that has to be rerouted. Due to size restrains, using a 1" pipe for the last 3 feet before it penetrates the roof would make my life much easier. Code issues? I want to do this right, not just easy. Thanks

Fixture vent sizing

Thought AAV's were not code in most places for dishwashers, due to the possible high flow rates. (however this seems bogus to me, with a 1 to 1 1/4" sink drain, a full (8-10" deep min 14x12") sink of water causes massive suction during drainage. How this can be less flow than a 3/4 drainline from a DW is beyond me. Maybe there's another reason?)